So, this silver ferrocyanide can react with sodium sulfide and give solver sulfide. So, this supposedly rehallogenating bleach will somehow work when toning prints, right? Silver sulfide is far less soluble than silver bromide.
So, this silver ferrocyanide can react with sodium sulfide and give solver sulfide. So, this supposedly rehallogenating bleach will somehow work when toning prints, right? Silver sulfide is far less soluble than silver bromide.This nails it:
"Silver ferrocyanide is extremely insoluble in water, its solubility being intermediate to that of silver chloride and silver bromide. Thus, silver chloride dissolves in solutions of potassium ferrocyanide with precipitation of silver ferrocyanide, whereas silver bromide and iodide do not."
If any silver chloride were to be formed by the ferricyanide+chloride bleach's action on silver, then it will dissolve due to the presence of potassium ferrocyanide in the bleach and precipitate silver ferrocyanide again. In other words, no silver chloride is formed and ferricyanide+chloride is not a rehalogenating bleach.
this supposedly rehallogenating bleach will somehow work when toning prints, right?
To overcome the problem of slow bleaching.Copper sulphate bleach is definitely more stable than permanganate bleach and it can be reused several times. I've used copper sulphate bleach for over a month after mixing without any noticeable instability. The biggest complaint I've about copper sulphate bleach is that it is slow and takes 15-30 minutes in some cases.
This nails it:
"Silver ferrocyanide is extremely insoluble in water, its solubility being intermediate to that of silver chloride and silver bromide. Thus, silver chloride dissolves in solutions of potassium ferrocyanide with precipitation of silver ferrocyanide, whereas silver bromide and iodide do not."
In summary, there should be no significant difference in the bleaching result of a plain ferricyanide bleach (non-rehologenating) and ferricyanide+chloride bleach. Now, chloride can act as a very mild blix and remove some density in the lightest regions of the film/print. So the results might not be exactly identical but pretty close.
Sigh. Okay, that's sufficient that I don't feel the need to even test it. Perhaps I could use an EDTA/chloride bleach (similar to C-41 bleach with sodium chloride added)? What's needed, clearly, is a bleach that produces a silver species that's more soluble than silver chloride. The answer might be on this chart.
@relistan Seemingly the only way to obtain silver acetate from image silver is with peracetic acid, which (based on recent reports in that thread) is inconsistent, tends to redeposit developable silver compounds that produce an effect similar to dichroic fog (the yellow stain), and due to gas evolution may be prone to damage soft emulsions. I was actually looking at silver salicylate on the solubility chart, and wondering if aspirin (cheap, safe to handle, low toxicity) acidified with acetic acid and doped with sodium chloride might have the desired effect -- or the aspirin/acetic solution act as a bleach independently, dispensing with the need for chloride.
I've got a long weekend starting tomorrow, I'll try to make up a test batch of salycilate bleach...
But your idea sounds very interesting and I'd love to see the experiment results!
@relistan wondering if aspirin (cheap, safe to handle, low toxicity) acidified with acetic acid and doped with sodium chloride might have the desired effect -- or the aspirin/acetic solution act as a bleach independently, dispensing with the need for chloride.
Without an oxidizing agent, a mix of salicylic acid, acetic acid and potassium chloride won't function as a bleach. And if you are going to use it with ferricyanide, are you sure it is safe?
I use Tim Rudman's copper bleach formula, it is slow but works well!
That's nice! There is a thread on using copper sulfate bleach in B&W reversal processing in case you're interested.
4- Tim Rudman copper bleach formula [http://real-photographs.co.uk/.../copper-sulfate-bleach/] 40min at 30ºC
7- Diluted ammonia bath. I use MrMusculo window cleaner that is 3% ammonia hydroxide solution for 2 hours.
@Raghu Kuvempunagar
Ammonia... I say 2 hours yes! I use the window cleaner that it says is 3% and also make testes at 15,30, 60 min and results are not optimal so I leave for 2 hours and the results are as expected. I still need to try an ammonium hydroxide solution, not window cleaner.
Nice looking images ! Thanks for sharing your process too.I use Tim Rudman's copper bleach formula, it is slow but works well! This is for one of my first tests using the copper reversal bath.
View attachment 264252
Looks interesting! Just curious, the yellow cast was from your backlight right?I use Tim Rudman's copper bleach formula, it is slow but works well! This is for one of my first tests using the copper reversal bath.
View attachment 264252
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